The invention relates to a device for adjusting stick-type blades in a cutter head, e.g., of the type used for milling or hobbing of spiral bevel gears.
These devices help the setter of a cutter head in aligning all blades with their tip cutting edges to an axial height which is as uniform as possible and at the same time in moving them with their profile cutting edges to a correct radial position in the cutter head. On the one hand, this should result in that the tip cutting edges in plunge cutting of tooth gaps remove chips of the same thickness and do not wear the individual projecting blades to an excess degree. On the other hand, in the generating process, all profile cutting edges will execute uniform profiling cuts so that a correct tooth profile is produced.
This adjustment process is necessary not only when the cutter head is first equipped with new blades, but also after each resharpening of the blades. Specifically, all blades must be dismounted from their chambers in the cutter head for sharpening, resharpened, and then re-installed exactly. Nevertheless, this tool system is economically advantageous since the stick blades can be resharpened many times only when the adjustment process is prompt, reliable and accurate. Therefore adjustment devices are used for support.
A device of this type is described for example in WO 97/07930. Accordingly, it was prior art that the blades were inserted by hand into the chambers of the cutter head, pushed with their tip cutting edges in the axial direction against a stop, and preferably clamped with pressing screws in their chambers. On this basis, the invention of WO 97/07930 relates essentially to the process for acquiring the radial position of each blade, the probe which is provided being located in a measurement plane which is offset from the axial plane of the cutter head. Sensing takes place therefore almost vertically on the lateral relieved surface of each blade. If it is ascertained that the radial position of the individual blade is outside the stipulated tolerance, these blades must be briefly released in the conventional manner in the cutter head, their tip cutting edges pressed by hand against the now correspondingly corrected stop, and screwed tight again.
The described manual displacement of the blades against the fixed stop consisting mostly of hard metal has the major defect that damage can easily occur on the tip cutting edges: On the one hand, when the cutter encounters the stop at an overly high speed, on the other, when the cutter is moved somewhat radially by screwing tight and/or is pressed axially with the tip cutting edge against the fixed stop. Damage can occur especially when the cutters themselves also consist of hard metal and their tip cutting edges are accordingly more sensitive.
The present invention can reliably prevent damage to the tip cutting edges when the blade is adjusted and in doing so nevertheless within a short time to achieve the required tolerance for the location of the blades in the cutter head. The cutter head may be one which is used for cutting, e.g., hobbing or milling of spiral bevel gears, each cutter or blade, e.g., stick-type blade, having a shaft, a tip cutting edge and at least one profile cutting edge. The cutter head includes a disk-shaped base or tool body with an axis of rotation, two parallel end faces, and a plurality of chambers which are located around the periphery and into which the respectively assigned blade with its shaft is pushed and releasably fixed. The device for adjusting such blades includes a frame, a numerically controlled turntable provided on the frame for coaxially supporting the cutter head, and a stable arm attached to the frame, the stable arm being movable at least axially and radially to the cutter head supported on the turntable and being numerically controlled and having, on its front end, a push head with which each blade can be pushed automatically into its chamber down to a stipulated height. At least one measuring device is provided for measuring positions of the push head relative to the frame. A probe is connected to the stable arm, the probe having at least one deflectable feeler which can be deflected perpendicular to one end face of the cutter head, the deflectable feeler having a sensing surface located in an immediate vicinity of the push head. The probe measures before, during and shortly after a blade is pushed in, positions of the tip cutting edge relative to the push head. An evaluation means is provided for evaluating the measured values of the measuring device and the probe to determine the attained height of the tip cutting edge of each blade relative to an end face of the disk-shaped tool body.
One main advantage of the device of the present invention is that it can automatically push the inserted cutters or blades into the stipulated axial position in the cutter head and in doing so works much more uniformly and accurately than is possible in manual setting. In particular, damage to the tip cutting edges is precluded by the push head with its pressure surface made as claimed in the invention coming down on the blade behind the tip cutting edge with a stipulated noncritical speed, while the sensitive tip cutting edge is touched only by the sensing surface of the probe which exerts a low measurement force of roughly 0.2 N. With the received measurement values not only is the insertion of the blades controlled, but also their final position in the cutter head is measured.
If, in one embodiment of the device, the turntable has a vertical axis of rotation, in the supported cutter head its chambers are also roughly vertical. This leads to the blades which have be inserted for adjustment being able to slip too far down. In this case it is provided that all blades are exposed to a friction force which is preferably applied by narrow leaf springs. They are all located in turn preferably on a thin disk which is matched to the size of the cutter head and which is seated on the cutter head before assembly so that one leaf spring projects into each chamber. If at this point the blades are inserted into the chambers, they are held by the leaf springs and nevertheless can be pushed down by the arm as claimed in the invention against a roughly constant friction.
A similar advantageous action is attained when instead of the narrow leaf springs in each chamber there is a coiled compression spring which is attached coaxially to that side of the existing pressing screw which presses against the blade and holds it. This embodiment of the invention has the additional advantage that each blade can also be exposed to the correct force when it is to take an altered radial location in the cutter head using a spacer plate in its chamber.
If in another embodiment of the invention a multicoordinate probe is used, a feeler combination with two feelers can be applied. While one is used as claimed in the invention to sense the tip cuffing edges in the axial direction, after clamping the blades in the cutter head, the other feeler can measure the location of the profile cutting edges in the radial direction. If this measurement shows that individual blades exceed the tolerance for the radial cuffing edge position, the device as claimed in the invention offers potential for simple correction of the cuffing edge position which will be detailed later.
In another embodiment of the invention the device is integrated in a conventional, numerically controlled multicoordinate measurement device which either already has a turntable or is retrofitted with one. In addition, on such a measurement device there is a carriage which carries the probe and which can be moved axially and radially to the turntable. When this carriage also acquires an arm with a push head, as claimed in the invention, all structural prerequisites for an adjustment device as claimed in the invention are met. Then the CNC control of the measurement device is provided with a software expansion and on the probe a corresponding feeler for axial measurement of the tip cutting edges is inserted in order to obtain a serviceable device as claimed in the invention.